The 2018 federal budget proposed by the White House would shrink critical tools—of diplomacy, development work and peacemaking—that can reduce the civil wars abroad that threaten U.S. interests and global stability. Forthcoming research for the American Academy of Arts and Sciences shows that these tools can be effective and cheaper than the military forces upon which we must rely when those wars flare into immediate threats. The international system for mediating and keeping peace in such conflicts must be strengthened and updated—not abandoned.